Normally tacky and pressure sensitive adhesive (PSA) materials have been used for well over half a century. Products of this type, which take the form of tapes, labels, and other types of adhesive coated sheets, must be protected from unintended adhesion to other surfaces. Hence, tapes are typically wound into a roll on their own backing and labels are typically laminated to a release sheet to prevent their accidental adhesion to other surfaces and also to prevent their contamination with air-borne dust and other contaminants.
In order to allow a roll of tape to be unwound without the undesirable transfer of adhesive to the tape baking, it is customary to provide the tape backing with a low adhesion backsize (LAB). Similarly, the release sheet or liner, to which the adhesive coated label is typically laminated, is supplied with a release coating to permit the easy removal of the liner from the label. This LAB or release coating is expected to reproducibly provide an appropriate level of release to the adhesive of interest, to not deleteriously affect the adhesive, and to be resistant to aging so that the release level remains relatively predictable with time.
Various polymers having low critical surface tension such as silicones, fluorine-containing polymers, and long alkyl chain branched polymers are useful as release coatings (e.g., LABs). Long alkyl chain branched polymers are waxy compounds that can be used to prepare release coatings of medium release value which are especially desirable for PSA tapes. Release coating patents also describe the use of silicone polyureas. Suitable silicone polyurea polymers typically include random blocks of polydimethyl siloxane, soft segments of polyethylene oxide or polypropylene oxide, and hard segments of a low molecular weight diamine/diisocyanate product. These can be water-borne or solvent-borne polymers and are typically applied to nonporous films.
There is a need, however, for low adhesion backsize coatings that can be applied to porous backings, such as nonwoven polypropylene backings.